The invention relates to an improvement in or modification of the sealant composition the subject of the present applicant's International (PCT) Application No. PCT/AU2007/001222.
A puncture can be a serious hazard associated with the use of inflatable load-carrying articles such as tyres—whether such be on automobiles, trucks, motorcycles, bicycles, etc. When a puncture occurs with an automobile, for example, the traditional practice has been to replace the damaged/punctured tyre with the spare, with such spare being intended to allow for use of the vehicle either only for a limited time and limited distance—to allow the driver to travel to a site where the damaged tyre can be repaired and restored to the vehicle—or in the alternative to allow the vehicle to be driven without problems until such time as a replacement or repaired tyre can be secured and installed.
There can be difficulties associated with, firstly, removal of a punctured tyre and, secondly, location of the spare or a replacement tyre on the vehicle. These difficulties can include the unavailability of the tooling needed to remove a damaged tyre and replace such with the spare, and the actual physical effort associated with such tasks, not to mention potential risks/damage to the person effecting such a task. Furthermore, the situation has been known to arise where the spare tyre may not be sufficiently inflated to be properly and safely usable.
In accord with the prior art practices there have been employed, for purposes of introduction of a sealing composition into a punctured tyre, an apparatus consisting of a pressurised container for the sealing composition which houses a liquefied gas—of any suitable type—as a pressure source. Such container includes, for purposes of dispensing the contents thereof, a valve or the like having associated or to be associated therewith an adaptor which allows for connection of the overall container to the tyre valve. Such an adaptor may be of the screw-on type, or of any other known type. With such an arrangement the sealing composition is sprayed into the tyre through the tyre valve, the tyre then being re-inflated by means of the propellant gas, which then allows the car to be driven.
In another known arrangement a sealing composition is housed within a compressible flask which is to be connected, via an adaptor of any known type, to the tyre valve, with the valve insert or core having first been removed therefrom. With such an arrangement the sealing composition is sprayed into the tyre by applying pressure to the compressible flask. After the valve core or insert has been replaced, the tyre can then be re-inflated as desired (using any suitable means and method). This method and arrangement suffers in that, to be carried out, it is necessary to physically remove the valve core or insert from the tyre valve itself.
In accordance with the known art there have also been used in the past sealant compositions, intended to be injected into a damaged tyre, useful for emergency (and almost invariably) temporary, repair of a puncture wound in the tread portion of such tyre. Such compositions have traditionally included latex (or the equivalent) as a principal constituent thereof. The compositions are intended to be injected into the tyre via the tyre valve (with or without valve core in place).
However the use of latex (or an equivalent) in itself has given rise to problems, due to the “sticky” nature thereof. Firstly, the use of latex will leave a sticky, messy residue in the tyre valve itself, which will more often than not need to be removed/cleaned away before that valve is re-useable. Secondly, the dispensation of a latex-based composition from a container therefor will mean that such container may not be suitable for re-use, again by reason of the fact that any nozzle or the like dispensing means associated therewith, and/or any tubing or hosing for passage of the sealing composition from container to tyre, will be gummed-up, perhaps even being blocked or sealed, by residual or undispersed composition.
Further, and when a latex-based composition is employed the situation is that, when air is still escaping from the tyre, via the puncture, and the latex composition is oozing (under pressure) through the hole in the tyre, the air causes the latex to cross-link and bond with the rubber of the tyre. The end result is that, whilst the puncture may be sealed, the actual puncture site becomes extremely difficult, if not actually impossible, to locate. This inability to identify a repaired puncture site gives rise to its own problems. In accordance with regulations, and indeed using common sense, if one knows of the existence of a puncture in a tyre, and even if that puncture has been temporarily repaired—using such a latex-based composition—it is still necessary to have the tyre properly, and permanently, repaired. If the site cannot be located, a permanent repair cannot be effected. The alternative, then, is to physically replace the tyre when punctured—an expensive exercise indeed.
There are environmental issues concerning latex and the use of latex-based compositions for purposes of temporary tyre repair which may be summarised as follows:
(1) the life or age limit of latex is usually 5 years;
(2) unless the puncturing object remains in the tyre it is virtually impossible to locate, inspect and repair the tyre permanently—to meet with safety regulations and standards the tyre must then be discarded;
(3) latex must not be allowed to enter sewerage/surface water or ground water;
(4) any used packaging contaminated with cured latex cannot be cleaned for recycling and therefore must be disposed of along with the substance;
(5) with latex, cleaning and washing the tyre is problematic; the tyre can only be cleaned by absorbing the liquid with cloth/rags and placing them in containers for waste disposal;
(6) latex emulsion gives off a strong ammonia vapour and is therefore not popular in tyre repair shops and the like, due to this noxious odour;
(7) latex emulsion has a pH value of 10 and, if contact occurs, can cause irritation to eyes, skin or mucous membranes;
(8) latex spills will permanently stain clothing or work garments unless the excess latex is immediately removed and the garments thoroughly washed before cross-linking occurs, which usually is not feasible;
(9) latex sealants ideally should be filled into bottles under a bed of nitrogen to minimise the cross-linking effects of oxygen on latex; any oxidation is detrimental to the sealing capacity of latex and also increases the possibility of granulated particles lodging in tyre valve; even occasional small droplets of latex carried by compressed air (or the like) in hoses can start “skinning” in the hose and can also end up agglomerating in the valve area; and
(10) latex contains volatile organic compositions which can be harmful to health if swallowed, cause acid burns, can cause sensitisation through skin contact and are highly toxic for aquatic organisms.
Apart from the problems associated with the prior art as outlined earlier, these days it is a trend in vehicle design that vehicles are being manufactured and marketed without being supplied with a spare wheel. This means that a practical, workable repair kit needs to be provided, such a kit being intended to be simple to operate, preferably re-usable and not requiring clean-up of excess sticky sealing compounds (as for example latex or the like).
The present invention seeks to overcome the problems and difficulties associated with the prior art practices by providing a composition and apparatus which allows for ready in situ repair—as by re-sealing—of a punctured tyre, thereby eliminating the need for replacement thereof (at least temporarily).
With the composition and apparatus of this present invention it is not necessary to remove the valve core or insert from the tyre valve. More importantly the composition of the present invention, by not including latex (or the equivalent), avoids the need for clean-up and disposal of residual unwanted material (latex) upon completion of any repair.
It will be understood, by those persons familiar with this art, that punctures which are capable of being effectively sealed with these types of compositions are those which occur in the substantial majority of cases to vehicle wheels in the course of normal usage, as for example, punctures to car and truck tyres by nails, screws, pieces of wire and the like.
It has been found that the addition of polyacrylates and other similar synthetic elastomers, and more particularly sodium polyacrylate, to known sealant compositions, and even to components for known sealant compositions, will give rise to an overall composition which will exhibit significantly enhanced sealing properties (when compared for example with those of the present applicant's aforementioned International Application).